The present invention relates to generally a pattern recognition system and more particularly a pattern recognition system capable of identifying the input patterns correctly even when an input pattern has a strong similarity with more than one standard patterns in storage for identification.
In a conventional superposition type pattern recognition system, an input pattern is superposed upon each of standard patterns of different categories in storage so that there may be established one-to-one correspondence between the input pattern and a number of the standard pattern which has the maximum similarity to the input pattern. The pattern recognition system of the type described is simple in construction so that it has been widely used in various fields especially when the characters and numerals to be identified have been standardized. The superposition type pattern recognition system is also used in order to identify the characters and numerals written within a predetermined space or block, but an additional operation for normalizing the deviation of a character or numeral from the standard is required. Furthermore, in the superposition type pattern recognition system, the overall input and standard patterns are compared with each other in order to determine the degree of similarity therebetween. Therefore, when the overall input and standard patterns are similar macroscopically, the similarity of the input pattern to the standard pattern is determined as strong even when they are apparently different from each other in minute points. As a result, an input pattern is identified as having strong similarity to two or more standard patterns so that identification of the input pattern becomes impossible.
One of the objects of the present invetnion is therefore to provide an improved pattern recognition system capable of correctly identifying an input pattern even when it exhibits strong similarity to more than one standard pattern of different categories in storage.
In general a human observer identifies a pattern such as a character first by discerning the overall configuration of this pattern and then distinguishing the specific features of the pattern when he sees that its overall configuration has strong similarity to more than one pattern so as to reach the final conclusion. The present invention may simulate this humane pattern recognition process.
According to one embodiment of the present invention, an input pattern is converted by an input device into electrical video signals, which are quantized and stored in a two-dimensional memory. The input pattern information stored in the memory is converted into a plurality of analog voltages representing the features of the input pattern. The analog voltages are applied to a similarity identification unit so that the degree of similarity of the input pattern to the standard patterns in storage may be obtained. In accord with the present invention, the similarity of the input pattern to each of the standard patterns is represented by an analog voltage. The analog output voltages are applied to an identification unit so that there may be established one-to-one correspondence between the input pattern and one of the standard patterns when only one analog output voltage representing said one standard pattern is in excess of a predetermined level. The above steps are similar to those of the conventional pattern recognition systems. According to the present invention, when the input pattern exhibits strong similarity to two of the standard patterns in storage, an input pattern enlargement control unit is actuated to enlarge a part of the input pattern so that the latter may be identified as belonging to one of the two standard patterns based upon the features extracted from the enlarged input pattern. However when the input pattern exhibits similarity to three or more standard patterns in storage, a signal representing the impossibility of identification of the input pattern (or rejection thereof) is generated.
The above and other objects, features and advantages of the present invention will become more apparent from the following description of one preferred embodiment thereof taken in conjunction with the accompanying drawing.